Message Handling

1. A method of handling messages at a user equipment received from a communications network during a procedure, the method implemented at the user equipment comprising: receiving a first message from the communications network whilst the user equipment is in a first operating state; processing the first message and entering a second operating state in response to receiving the first message; receiving a second message from the communications network whilst the user equipment is in the second operating state; detecting that the second message is a duplicate of the first message; and checking for an indication that the second message is a potential duplicate of the first message, the indication based on re-establishment of a signaling radio bearer; wherein: if said indication is not present, the method comprising transmitting a failure notification to the communications network; and if said indication is present, the method comprising discarding the second message and not transmitting a failure notification to the communications network to prevent failure of said procedure.

2. The method of claim 1 , wherein the user equipment is unable to process the second message whilst in the second operating state.

3. The method of claim 1 , wherein the user equipment communicates with the communications network in accordance with a multi-layered communication protocol comprising a Non-Access Stratum (NAS) and said steps of claim 1 are implemented by a NAS entity.

4. The method of claim 3 , wherein the first message is a NAS message and the second message is a NAS message.

5. The method of claim 3 , wherein said step of checking for an indication that the second message is a potential duplicate of the first message comprises determining if the second message was detected as potentially being a duplicate of the first message prior to receiving the second message.

6. The method of claim 5 , wherein said step of determining comprising the NAS entity determining if it had received said indication from a Radio Resource Control (RRC) layer of the multi-layered communication protocol prior to receiving the second message.

7. The method of claim 6 , wherein the RRC layer is configured to transmit said indication to the NAS entity responsive to initiating a re-establishment, in a Radio Link Control (RLC) layer of the multi-layered communication protocol, of a signaling radio bearer used to transport NAS messages.

8. The method of claim 3 , wherein said step of the NAS entity checking for an indication comprises determining if an indication is attached to the second message, said indication identifying that the second message is a potential duplicate of the first message.

9. The method of claim 8 , wherein the NAS entity receives the second message from the communications network via a Radio Resource Control (RRC) layer of the multi-layered communication protocol.

10. The method of claim 9 , wherein the RRC layer attaches said indication to the second message and supplies the second message together with said indication to the NAS entity if the second message is the first NAS message to be received from the communication network after the RRC layer initiating a re-establishment, in a Radio Link Control (RLC) layer of the multi-layered communication protocol, of a signalling radio bearer used to transport NAS messages.

11. The method of claim 9 , wherein the RRC layer of the multi-layered communication protocol does not attach said indication to the second message if the second message is not the first NAS message to be received from the communication network after the Radio Resource Control (RRC) layer initiating a re-establishment, in a Radio Link Control (RLC) layer of the multi-layered communication protocol, of a signalling radio bearer used to transport NAS messages.

12. The method of claim 3 , wherein the first operating state is a first protocol state associated with the NAS entity and the second operating state is a second protocol state associated with the NAS entity.

13. The method of claim 3 , wherein the procedure is a call establishment procedure, and the NAS entity is a Call Control entity.

14. The method of claim 13 , wherein the first operating state is a first call control protocol state and the second operating state is a second call control protocol state.

15. The method of claim 3 , wherein the NAS entity is one of: a Short Message Service (SMS) entity; a Supplementary Services (SS) entity; a Session Management (SM) entity; and a Mobility Management (MM) entity.

16. A user equipment comprising: a transceiver operable to access a communications network; a central processing unit; and a memory coupled to the central processing unit, the memory containing program code executable by the central processing unit causing the central processing unit to perform the following steps: in response to receiving a first message from the communications network via the transceiver whilst the user equipment is in a first operating state, process the first message causing the user equipment to enter a second operating state; in response to receiving a second message from the communications network via the transceiver whilst the user equipment is in the second operating state, detect that the second message is a duplicate of the first message; and check for an indication that the second message is a potential duplicate of the first message, the indication based on re-establishment of a signaling radio bearer; wherein: if said indication is not present, transmit a failure notification to the communications network via the transceiver; and if said indication is present, discard the second message and not transmit a failure notification to the communications network to prevent failure of said procedure.

17. A computer program product for handling messages at a user equipment received from a communications network during a procedure, the computer program product comprising code embodied on a non-transient computer-readable medium and configured so as when executed on a processing unit of the user equipment to perform the steps of: receiving a first message from the communications network whilst the user equipment is in a first operating state; processing the first message and entering a second operating state in response to receiving the first message; receiving a second message from the communications network whilst the user equipment is in the second operating state; detecting that the second message is a duplicate of the first message; and checking for an indication that the second message is a potential duplicate of the first message, the indication based on re-establishment of a signaling radio bearer; wherein: if said indication is not present, the method comprising transmitting a failure notification to the communications network; and if said indication is present, the method comprising discarding the second message and not transmitting a failure notification to the communications network to prevent failure of said procedure.

18. The computer program product of claim 17 , wherein the user equipment is unable to process the second message whilst in the second operating state.

19. The computer program product of claim 17 , wherein the user equipment communicates with the communications network in accordance with a multi-layered communication protocol comprising a Non-Access Stratum (NAS) and said steps of claim 1 are implemented by a NAS entity.

20. The method of claim 19 , wherein the first message is a NAS message and the second message is a NAS message.